A variety of cutter or bits are known in the art of mechanical excavation. One type of cutter commonly used on large diameter cutterheads in rock excavation is the disc type rolling cutter. Disc cutters are presently frequently used on cutterheads employed in tunnel boring, raise drilling, and large diameter blind drilling.
In hard rock the disc type cutter operates on the principle that by applying great thrust on the cutter, and consequently pressure on the rock to be cut, a zone of rock directly beneath (i.e., in the cutting direction) and adjacent to the disc cutter is crushed, normally forming very fine particles. The crushed zone forms a pressure bulb of fine rock powder which exerts a hydraulic like pressure downward (again, the cutting direction) and outward against adjacent rock. The adjacent rock then cracks, and chips spall from the rock face being excavated.
The present invention is directed to a novel disc cutter which dramatically improves production rates of disc cutter excavations which also allows reduced thrust requirements for cutterhead penetrations, which in turn reduces the weight of the structure required to support the cutters. Such reductions also allow disc cutter technology to be applied to novel, small diameter cutterheads for excavation equipment. Additionally, the relatively light weight of our disc cutters provides dramatically decreased parts and labor costs for the maintenance and replacement of cutterhead wear parts.